1. Field of the Invention
The present invention relates to a communication apparatus provided with synchronous transfer function and asynchronous transfer function, a method and a digital interface therefore.
2. Related Background Art
Recently various developments have been made to connect various digital devices such as a personal computer, a printer, a hard disk, a digital camera, a digital video camera, etc., with a high-speed digital interface common to these devices.
Among the high-speed digital interfaces developed for such objective, there is known a digital interface based on the IEEE1394-1995 standard (hereinafter called 1394 interface). The detailed explanation on the IEEE1394-1995 standard is disclosed in the IEEE Standard for a High Performance Serial Bus (IEEE Std 1394-1995), approved and published by the IEEE (Institute of Electrical and Electronics Engineers, Inc.) Standard Committee.
The 1394 interface is superior to the conventional digital interface in certain characteristic features, and one of such features is that the 1394 has two transfer modes, namely xe2x80x9cisochronous transfer modexe2x80x9d and xe2x80x9casynchronous transfer modexe2x80x9d.
The transmission packets based on these transfer modes are multiplexed on time-shared basis within a predetermined communication cycle (for example 125 xcexcs). The isochronous transfer mode provides data transfer of a constant amount for each communication cycle, and effectively transfers data that has to be transmitted in continuous manner with a constant data rate, such as video data or audio data. The asynchronous transfer mode executes data transfer in asynchronous manner relative to the predetermined communication cycle, and effectively transfers data that is transferred non-periodically, such as control commands or file data.
Another feature is the function of constructing a bus-type network and relaying a packet, transmitted from a 1394 interface to another 1394 interface. Based on this function, a packet transmitted by the isochronous or asynchronous transfer mode can be transferred to the 1394 interfaces of all the digital devices on the network.
FIG. 1 shows the configuration of a conventional 1394 interface and of a digital device equipped with such 1394 interface.
In FIG. 1 there is shown a physical layer (Phy) 101 based on the IEEE 1394-1995 standard, having the functions of initialization (automatic recognition of connection configuration of the system and automatic setting of communication ID of the devices) in response to a change in the connection configuration of the system, arbitration of the bus use right, relaying of data to another node, encoding of a serial signal, output/detection of the bias voltage, etc. The physical layer 101 is provided with two communication ports 102, 103 each of which is connected to an external network through a twisted pair cable 104 based on the IEEE 1394-1995 standard. The twisted pair cable 104 serially transmits the digital information encoded by the DS-link encoding method in a digital device connected to the network.
A transmitter unit 105 transmits a packet, packetized according to the isochronous or asynchronous transfer mode, in a predetermined communication band. A transmission packet memory 107 is connected between the transmitter unit 105 and a transaction process unit 109 and stores a packet, packetized in the transaction process unit 109 based on the isochronous or asynchronous transfer mode. A receiver unit 106 sends a packet, received through the network, to a succeeding reception packet memory 108. The reception packet memory 108 is connected between the receiver unit 106 and the transaction process unit 109, and stores a packet received from the external network.
The transaction process unit 109 is connected, through an internal interface 110, to a system bus 111 provided singly in the digital device. The system bus 111 is connected to various process units 112-117 provided inside the digital device and adapted to execute predetermined processes on the digital data received from an external device or outputted from these process units.
The internal interface 110 of the 1394 interface 112 manages the digital data supplied from or to be supplied to the process units (113 to 117) connected to the system bus 111.
The process units connected to the system bus 111 include, for example, an image processing unit 113 for effecting data processing for displaying image data of a predetermined data format, an isochronous data transmission/reception control register (Iso Tr. Reg.) 114, a bus management register (CSR""s) 115, a memory 116, and a control unit 117 equipped with a microcomputer and adapted to control the various process units within the digital device. The system bus 111 shown in FIG. 1 can be composed, for example, of a PCI bus.
The digital device provided with the 1394 interface of the above-described configuration has been associated with the following drawbacks.
In the above-described configuration, any data transmitted (or received) according to either of the two (isochronous and asynchronous) transfer modes must first be stored in the transmission packet memory 107 (or reception packet memory 108) which is singly provided in the device. For this reason, there is required complex control or management of the timing of data write-in or read-out based on either transfer mode.
Also, any data transmitted (or received) according to either of the two transfer modes must be processed through the transaction process unit 109, the internal interface 110 and the system bus 111, each of which is singly provided in the device. For this reason, with an increase in the frequency of communication with other digital devices, the data amount supplied from the transaction process unit 109 and other process units 113-117 to the system bus 111 increases, resulting in increased traffic therein.
In particular, in case of transmitting (or receiving) data requiring a high data transfer rate and real time processing, such as moving image data, the complete processing of such data may become impossible depending of the traffic status of the system bus 111. As a result, there may be encountered a situation where the internally processed moving image is interrupted in the course of processing or the transmission (or reception) has to be repeated from the beginning.
An object of the present invention is to solve the above-described drawbacks.
Another object of the present invention is, in a communication apparatus, a method and a digital interface therefor, to reduce complexity of the communication process in the digital device and to realize smooth communication with an external network.
As a preferred embodiment for such objects, the present invention discloses a communication apparatus comprising;
a communication unit having a first communication mode and a second communication mode;
a first unit for processing data transmitted or received utilizing a first internal bus and based on the first communication mode; and
a second unit for processing data transmitted or received utilizing a second internal bus and based on the second communication mode.
As another embodiment for such objects, there is a communication apparatus comprising:
a reception unit for receiving data transmitted in plural different communication modes;
plural memories for storing data, received by the reception unit, respectively for the plural different communication modes; and
plural process units for processing data, stored in the plural memories, respectively for the plural different communication modes.
As still another embodiment for such objects, there is disclosed a communication apparatus comprising:
a first communication unit for controlling transmission/reception based on a first communication mode;
a second communication unit for controlling transmission/reception based on a second communication mode; and
a setting unit for setting transmission/reception based on the second communication mode, utilizing the communication mode.
As still another embodiment for such objects, there is disclosed a communication apparatus comprising:
a communication unit having a synchronous transfer mode and an asynchronous transfer mode;
a first internal bus for supplying data transmitted or received in the synchronous transfer mode; and
a second internal bus for supplying data transmitted or received in the asynchronous transfer mode.
As still another embodiment for such objects, there is disclosed a digital interface comprising:
a first communication unit for controlling transmission/reception based on a synchronous transfer mode;
a second communication unit for controlling transmission/reception based on an asynchronous transfer mode;
a first memory for temporarily storing data transmitted or received in the synchronous transfer mode; and
a second memory for temporarily storing data transmitted or received in the asynchronous transfer mode.
As still another embodiment for such objects, there is disclosed a communication method comprising steps of:
discriminating whether to execute a first communication mode or a second communication mode;
processing data transmitted or received by the first communication mode, utilizing a first internal bus; and
processing data transmitted or received by the second communication mode, utilizing a second internal bus.
As still another embodiment for such objects, there is disclosed a communication method comprising steps of:
receiving data transmitted by plural different communication modes;
storing the received data in plural memories respectively for the plural different communication modes; and
processing the data stored in the plural memories respectively for the plural different communication modes.
As still another embodiment for such objects, there is disclosed a communication method comprising steps of:
controlling transmission and reception based on a first communication mode;
setting transmission and reception based on a second communication mode, utilizing the first communication mode; and
controlling transmission and reception based on the second communication mode.
As still another embodiment for such objects, there is disclosed a communication method comprising steps of:
effecting transfer based on a synchronous transfer mode and an asynchronous transfer mode;
supplying data transmitted or received in the synchronous transfer mode to a first internal bus; and
supplying data transmitted or received in the asynchronous transfer mode to a second internal bus.
Still other objects of the present invention, and the advantages thereof, will become fully apparent from the following detailed description of the embodiments.